Today, most tire manufacturers utilize computer-controlled equipment and processes to manufacture vehicle tires. The use of such equipment and processes would, seemingly, lead to the production of vehicle tires which are virtually identical or uniform. Each vehicle tire, however, may be slightly different and have slightly different properties due to variations in the specific rubber, cording, and other materials used to produce the tire.
The non-uniformity of properties, or irregularities, in vehicle tires generates certain forces (sometimes referred to herein as “tire non-uniformity forces”) on a vehicle when the tires are mounted on a vehicle and the vehicle is driven under different conditions. These non-uniformity forces excite vehicle vibration. The perception of a vehicle's driver to such vibrations are affected by two major factors: the magnitudes of the non-uniformity forces and vehicle sensitivities to such non-uniformity forces. However, other factors may also effect the perception of a vehicle's driver to such forces. The tire non-uniformity forces are typically repeated with each revolution of a tire and are often periodic corresponding to primary tire rotation frequency (referred to herein as “first order”) or other higher order frequencies such as two, three, or fourth order frequencies (referred to herein as “high order”). Each vehicle may have many resonant frequencies in its chassis, frame, suspension system, steering linkage, and other components and subsystems which might be easily excited by the tire non-uniformity forces at certain vehicle speeds. These resonant behaviors of the system/subsystem may also affect the sensitivity of a vehicle.
For vehicle manufacturers, it is desirable to minimize a vehicle's sensitivity and, thus, the driver's perception to the vibration caused by such tire non-uniformity forces. Typically, vehicle manufacturers have to measure a vehicle's sensitivity by first testing the vehicle with different sets of tires having different levels of tire non-uniformity forces (including, without limitation, first and higher order force levels). Then tires are selected for the vehicle which generate acceptable non-uniformity forces and which provide acceptable vibration levels as measured by accelerometers and/or other sensors mounted at the vehicle's steering wheel and seat track. Unfortunately, the selection of tires which have such attributes is a very time-consuming and costly process since a large number of tires (possibly, hundreds of tires) may have to be sorted using high-speed uniformity testing machines in order to find an acceptable set of tires. The selection process is further exacerbated when it is necessary to find tires that produce high vertical non-uniformity forces and low horizontal non-uniformity forces or that produce certain ratios of such forces.
Therefore, there exists in the industry, a need for devices and methods for simulating tire non-uniformity forces during vehicle vibration sensitivity testing and for testing vehicle sensitivities to tire non-uniformity forces, and that addresses these and other problems or difficulties which exist now or in the future.